Older sing-box versions fail on 'close_timeout' in MTProto inbound
(added in Tachyon to fix SIGHUP hot-reload crash, issue #15).
Instead of hard-failing, runtime.uc now detects 'json: unknown field'
errors from sing-box check, strips the offending inbound field from
all inbounds in the generated JSON, and retries the check once.
This makes Tachyon forward-compatible: new fields for newer sing-box
versions degrade gracefully on older installs without requiring manual
version detection or config changes.
Dushnilin
3b1eb89124